21407207 has 4 divisors (see below), whose sum is σ = 21929376. Its totient is φ = 20885040.

The previous prime is 21407189. The next prime is 21407213. The reversal of 21407207 is 70270412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21407207 - 2¹² = 21403111 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21407257) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 261023 + ... + 261104.

It is an arithmetic number, because the mean of its divisors is an integer number (5482344).

Almost surely, 2^21407207 is an apocalyptic number.

21407207 is a deficient number, since it is larger than the sum of its proper divisors (522169).

21407207 is an equidigital number, since it uses as much as digits as its factorization.

21407207 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 522168.

The product of its (nonzero) digits is 784, while the sum is 23.

The square root of 21407207 is about 4626.7923013682. The cubic root of 21407207 is about 277.6642730515.

Adding to 21407207 its reverse (70270412), we get a palindrome (91677619).

The spelling of 21407207 in words is "twenty-one million, four hundred seven thousand, two hundred seven".